A hinge structure including a spring configured to assist an opening operation of a lid has been proposed (for example, see JP 2948538 B2 (hereinafter referred to as “Document 1”)).
The hinge structure described in Document 1 is a structure in which a lower hinge piece which is to be attached to a container and an upper hinge piece which is to be attached to a lid are pivotably connected to each other via a shaft. This hinge structure includes a torsion coil spring located to surround the shaft and is configured to generate spring force for assisting the opening operation of the lid by the torsion coil spring.
Since the hinge structure described in Document 1 is a structure in which the spring force is generated by the torsion coil spring, it is possible to prevent the entire hinge structure from largely protruding from the lid.